Abrasive blasting apparatus



Dec. 22, 1964 G. w. PQWELL ETAL 3,161,991

ABRASIVE BLASTING APPARATUS Filed Jan. 14, 1963 3 Sheets-Sheet 1 I V INVENTORS George WPaweZL Maxwell E Fahr lazy ATTORNEYS Dec. 22, 1964 e. w. POWELL ETAL 3,161,991

ABRASIVE BLASTING APPARATUS Filed Jan. 14, 1963 3 Sheets-Sheet 5 i i j m V/ 135N111] {4 l/ Mwweumuhmc 1+ .Qi AM ATTORNEY-5 United States Patent 3,161,991 ABRASIVE ELASTING APPARATUS George W. Powell and Maxwell E. Fahrney, Hagerstown,

Md., assignors, by mesne assignments, to The Pangborn Corporation, Hagerstown, MIL, a corporation of Delaware Filed Jan. 14, 1953, Ser. No. 251,101 10 Claims. (Cl. 51-9) The present invention is a continuation-in-part of co pending application Serial No. 80,587, filed January 4, 1961, now Patent No. 3,081,580, granted March 19, 1963, relating to apparatus for subjecting work pieces to a blast of abrasive particles, and particularly to such apparatus in which the work pieces are tumbled in a trough-shaped conveyor to expose all their surfaces for such blasting.

Among the objects of the present invention is the provision of a novel type air separator for the above apparatus.

A further object of the present invention is to provide a novel type abrasive recirculation assembly for the above apparatus.

The above, as well as additional objects of the present invention, will be more clearly understood from the following description of several of its exemplifications, reference being made to the accompanying drawings wherem:

FIGURE 1 is a partly broken away side view of one form of abrasive blasting apparatus illustrative of the present invention;

FIGURE 2 is a front elevation of the FIGURE 1 apparatus;

FIGURE 3 is a detail of a portion of the apparatus of FIGURES l and 2;

FIGURE 4 is a detail of an embodiment of the apparatus of the above figures; and

FIGURE 5 is a detail showing an embodiment of the air separator shown in FIGURE 1.

According to the parent application Serial No. 80,587, filed January 4, 1961, a blasting apparatus is disclosed which generally has a conveyor arranged to move through a path that forms a laterally tilted trough in which the work pieces are held and tumbled while they are blasted, and a housing around the conveyor keeps the blastant particles confined against escape into the surroundings. A doorway is provided through which to load and unload the work pieces and by inclining the doorway so that it faces upwardly above the conveyor, heavy work pieces can be loaded by an overhead crane if desired. Also the lower portion of the doorway is desirably tilted so as to face downwardly, thereby allowing work pieces to drop directly from the conveyor when they are to be unloaded.

The doorway is very carefully sealed inasmuch as the escape of flying particles can be hazardous to adjacent personnel, and in addition walking on a floor upon which such ball-like particles have dropped is likely to cause a fall.

The matter claimed in the parent application is directed to the above combination with emphasis on the door, door track and a deflector plate adjacent the lower portion of the door track.

As mentioned above, the objects of the present invention ahe directed to the abrasive-fines separator, an abrasive recirculation system and other features in combination therewith.

Turning now to the drawings, the apparatus of FIG- URES 1 and 2 includes a housing generally indicated at 20, within which is suitably supported an endless conveyor belt 22 so that it has an upper flight 24 and a lower flight 26. The upper flight is held by rotatable guide discs 28 so that it takes the shape of a trough inclined sideways, as shown in U.S. Patent No. 2,716,310. The

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conveyor belt is actuated by a driving motor 30 so that the upper flight 24 moves from the low side of the trough to the high side when Work pieces are to be subjected to the blasting treatment. A throwing wheel 32 or a set of such wheels, actuated by one or more motors 33 mounted on the housing roof above the trough, projects the abrasive blastant particles on the work pieces as they are caused to tumble on the upper flight during its upward travel. When the work pieces are to be unloaded the blastant projection is stopped as by a shut-off valve 35 in a conduit that supplies the blastant particles to the wheel, and the conveyor belt 22 is actuated to move in the reverse direction. This reverse movement carries the work pieces up over the lower edge 34 of the trough so that they will drop off the conveyor belt.

Below this lower trough edge the housing 20 has its front wall 36 recessed somewhat so as to allow the unloaded work pieces to drop down in front and outside the housing where they can be collected in a tote box or other suitable container, not shown. Above the front housing wall 36 the housing is provided with a door assembly slidably mounted in side tracks 40, 41. The lowest portion 43 of the tracks is inclined so as to provide a doorway that faces downwardly and through which the unloading work pieces can be discharged. The trackway curves back from this lowest portion to an intermediate section 45 which is inclined to provide an upper trackway that faces upwardly. Through the doorway formed by trackway section 45, work pieces can be loaded onto the conveyor. The tracks continue on to an uppermost section 47 which in the construction of FIGURE 1 is vertically positioned so as to keep from obstructing the space above the housing.

The door assembly consists of an upper rigid one-piece door panel 49 carrying rollers 51, 52 at its upper and lower ends in each of the tracks. From the lower end of this panel a flexible door panel 54 depends. This flexible panel is conveniently made of natural rubber or synthetic rubber, plastics or even with mesh as in U.S. Patent No. 2,716,310, or other flexible material, and can be stiffened by transverse stifleners, as shown and claimed in the parent application, spaced from each other to keep the side edges of the lower door from being pulled out of the trackways. To this end the stiffeners are provided with rollers 56 on each end and these rollers fit in the trackways.

The door assembly is operated by a pair of cables 61 each having one end secured to a lifting bracket 63 on the respective sides of the upper door panel, the other ends of the cables being threaded through reversing pulleys 65 and onto a hoisting drum 67. This drum can be electrically operated to wind up the cable and thereby lift the door assembly so as to expose the lower and upper doorways at 43 and 45. A one-way drive such as a worm gear type speed reducer in the drive connection from the motor will keep the door from dropping when the lifting action is terminated. A magnetic brake in the drive connection will also guard against such undesired dropping. Reversing the motor or disconnecting the one-way drive will permit the door assembly to descend.

The construction also includes a deflector plate fixed in place across the interior of the lower trackway just below the conveyor edge 34. The deflector plate should be sturdy enough to resist impacts from heavy work pieces and is mounted so as to form a deflector for abrasive particles that drop down through the slats of the conveyor at edge 34. Under some circumstances work pieces tend to become pinched between the adjacent slats of the conveyor and tend to be carried around along the lower flight of the conveyor rather than to drop free of its outer- I most edge. Such pinched work pieces are liberated by 3 the deflector plate and thereby kept from following the lower flight into the interior of the housing bottom.

The lower portion of the housing 28 tapers down to provide a hopper 106 through which the blastant particles are guided to a recycling mechanism which may, for example include a screw conveyor 10% located at the bottom of the hopper. The screw conveyor, or for that matter a vibrating conveyor, can be used to propel the particles to one side of the housing where they can be lifted by a bucket elevator 110 in the conventional fashion, and dropped into a separator 112 mounted on the top of the housing. The separator can include a scalping or separator drum 113 for separating heavier objects, such as wire rods, etc.

The details of the separator are shown in FIGURE 1 and is arranged to cause the recycled blastant particles along with .any fine materials that accompany them, to drop through a moving air stream in the separation cham her, as indicated at 118, so that the line materials are swept to one side along with the air stream. The heavier particles drop into storage bin 129 which in turn feeds the throwing wheel .32. The air stream is provided by a source of suction shown as duct 122 with a branched connection 124 leading through a battle chamber 126 and to a screened opening 128' on one face of the lower portion of the separator. Suction in source 124 sucks air in from screen opening 128 through abrasive stream 118. Air as well .as lighter particles such :as sand and fines continue through duct 129. A deflector 'baflie 130 directs air upwardly, and the duct being curved on top, the particles are swept around as in a cyclone collector. The particles follow along another baifle 131'and are deflected oli its lower end into expansion chamber 126, where the heavier of the swept along particles fall into spout 133, and the lighter particles are carried by the air to pipe 124 and on to a filtered or unfiltered discharge outlet for the air. The particles dropped into conduit 133 discharge at some convenient place where a collector such as a discharge bin 135 can be conveniently located, and removed when necessary.

The separator is equipped with a nozzle 136 inserted in screen opening 128 and tapered in such a manner as to increase the speed with which the sucked in air moves across the dropping particle stream 118.

The nozzle can also have its outer end connected to a blower 200 (FIGURE or other source of air under pressure to also increase the speed of travel across the dropping particle stream. Where the nozzle 136 is so supplied with air under pressure, it need not be tapered. To supply air under pressure, amanifold'201 can be fitted to cover opening 128, and a supply duct connected to the manifold adjacent one edge of the opening. A relatively small supply duct 202 connected to such a manifold for example, adjacent .a short end of a rectangular opening 128 having a relatively large width, will adequately supply pressurized air through the manifold over the entire width of the opening, it the duct is directed at right angles to the axis of the opening so that the pressurized narrow air stream changes direction to go through the opening.

An overflow conduit 137 is provided at the remote end of the separator to carry particles that reach that end so as to indicate that the separator is operating at full capac ity. Another conduit 139 is located with its upper end near the top of storage bin 120 so as to indicate by overflow of the particles when the storage bin is full. Both conduits can be arranged to have transparent sections or air gapsso that the movement of particles through them is readily observed. These conduits can lead directly to the screw conveyor or to the housing so that the particles passing through them are not removed from the system. A refuse conduit 141 is also conveniently provided for carrying ofi larger objects such as core wire, rods, etc., that the scalping drum 113 separated from the falling particles.

Suction source 122 is also connected by duct 145 to the interior of the housing 20 so as to withdraw air-carrying dust and the like that is present in the housing as a result of the blasting operation.

In directly knocking out sand cores in addition to other matter which adheres to castings, an excess amount of sand usually accumulates in the abrasive-refuse being circulated back to the blasting wheel for reuse therein. One pass of the abrasive-refuse through the separator has generally not been suflicient to separate all of the sand or refuse from the abrasive. The present invention provides means for recirculating the abrasiverefuse material so that it is given a treatment in the various separator units to more thoroughly separate the abrasive. To accomplish the above, a recirculating spout 205 leads oif from the supply hopper 120 and connects with the hopper overflow 139. When the valve-gate assembly 35 for the blasting head 32 is closed, the supply of abrasive to the blast wheel 32 is terminated. During this termination, the valve-gate 2% in the hopper overflow line (see FiGURE 3) is opened, and abrasive accumulated in the supply hopper pass through the recirculating spout 295 into the hopper overflow line 139 and through the valve-gate 206 for the overflow 139 from which point it is dropped by gravity through line 1'39 to the rotary screw 168. From this point, it is then raised by the elevator 11% and passes back into the normal separating system described above.

If desired, a surge tank 21% (FIGURE 4) maybe installed in the overflow line 139 to prevent any jam-up during surge or overfeed of the abrasive into the overflow line.

Another feature of the construction of FIGURES 1 and 2 is an additional separator in the lower portion of the housing. In FIGURE 1 a screen 151 is mounted across the hopper bottom 1% in a tilted position so as to catch large objects such as cores and wires, and keep them from going through the recycling system Where they might cause jamming. The tilting of the screen 151 causes such large articles to drop to the lowermost portion of this screen where the articles collect. Just above this lowermost portion an access door 153 is provided in the inclined bottom of the housing so that an operator can reach in and remove the objects collected by screen 151. The access door is shown as fitted across the interior of an opening 155 and overlapping the entire periphery of the opening so as to keep blastant particles from dropping through the opening both when the access door is open and when it is shut. Additional protection against the dropping of particles is provided by a baflle 157 above and spaced from the upper portion of the access door to keep falling particles from becoming caught on the upper edge of that door when the door is closed. The access door is also shown as hinged at 159 adjacent its upper edge by means of an arm 161 secured to the door and extending out through the opening. The arm terminates in a handle 163 by which the door can be operated.

Grasping the handle 163 and lowering it causes the access door to be raised. At the same time it is a simple matter to reach in through the doorway thus opened and pull out the objects on the bottom of screen 151 while the access door is held open. With this arrangement it is a simple matter to clean out objects collected by screen 151, whether the machine is in operation or not, and even While blasting is going on, care being taken for the operator reaching in to Wear suitable gloves to protect his hands against flying blastant. Because the presence of the lower screen 151, the scalping drum 113 of the separator 112 can be made smaller so that the entire height of the apparatus can be reduced.

Obviously many other modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In an apparatus for separating blastant particles from admixture with particles of lighter materials by sucking air across a falling curtain of said admixture in a separation chamber to cause the air to blow the lighter particles more to one side of the curtain than the blastant particles, and separately collecting the more deflected particles, the improvement according to which air velocity increasing means is in said separation chamber causing the air sucked into said separation chamber to increase its speed as it moves across said curtain, said velocity increasing means including an air inlet for the sucked in air said air inlet being provided with a nozzle that tapers over a substantial portion of its length that gradually reduces the cross sectional area of the air stream as it moves through the nozzle and thereby increases the speed of the air as it moves across the curtain.

2. In an apparatus for separating blastant particles from admixture with particles of lighter materials by sucking air across a falling curtain of said admixture in a separation chamber to cause the air to blow the lighter particles more to one side of the curtain than the blastant particles, and separately collecting the more deflected particles, the improvement according to which air velocity increasing means is in said separation chamber causing the air sucked into said separation chamber to increase its speed as it moves across said curtain, said velocity increasing means including an air inlet for the sucked in air said air inlet being provided with a blower connected to blow air into the inlet and thereby increase the speed of the air as it moves across the curtain, said air inlet being generally planar with a width that is large in relation to its height, a manifold being connected across the entire width, and said blower being connected to blow into one end of said manifold in a direction at right angles to the axis of said inlet.

3. In an apparatus for tumbling a batch of work pieces comprising a trough-shaped conveyor on which the work pieces are tumbled, a housing enclosing said conveyor, a loading and unloading doorway for said housing, abrasive particle blasting means extending into said housing for projecting abrasive against the work pieces, and an air separator for separating blastant particles from admixture with particles of lighter material by sucking air across a falling curtain of said admixture in a separation chamber to cause the air to blow the lighter particles more to one side of the curtain than the blastant particles and separately collecting the more deflected particles, the improvement according to which air velocity increasing means is in said separation chamber causing the air sucked into said separation chamber to increase its speed as it moves across said curtain, said velocity increasing means including an air inlet for the sucked in air, said air inlet being provided with a nozzle that tapers over a substantial portion of its length that gradually reduces the cross sectional area of the air stream as it moves through the nozzle and thereby increases the speed of the air as it moves across the curtain.

4. In an apparatus for tumbling a batch of work pieces comprising a trough-shaped conveyor on which the work pieces are tumbled, a housing enclosing said conveyor, a loading and unloading doorway for said housing, abrasive particle blasting means extending into said housing for projecting abrasive against the work pieces, and an air separator for separating blastant particles from admixture with particles of lighter materials by sucking air across a falling curtain of said admixture in a separation chamber to cause the air to blow the lighter particles more to one side of the curtain than the blastant particles and separately collecting the more deflected particles, the improvement according according to which air velocity increasing means is in said separation chamber causing the air sucked into said separation chamber to increase its speed as it moves across said curtain, said velocity increasing means including an air inlet for the sucked in air, said air inlet being provided with a blower connected to blow air into the inlet and thereby increase the speed of the air as it moves across the curtain, said air inlet being generally planar with a width that is large in relation to its height, a manifold being connected across the entire width, and said blower being connected to blow into one end of said manifold in a direction at right angles to the axis of said inlet.

5. An apparatus for tumbling a batch of work pieces comprising a trough-shaped conveyor on which the work pieces are tumbled, a housing enclosing said conveyor, a loading and unloading doorway for said housing, abrasive particle blasting means extending into said housing for projecting abrasive against the work pieces, a separator assembly for separating used abrasive from foreign matter picked up by the abrasive during the blasting operation, a supply hooper connected with the separator for receiving the separated abrasive from the separator, said blasting means being connected to said supply hopper, second pass separation means connected with the hopper for recirculating to the separator assembly a portion of the abrasive accumulated in the supply hopper for separating remaining foreign matter not separated during a prior pass through said separator assembly, said second pass separation means including an overflow conduit connected with the supply hopper, and a recirculating conduit connecting both the supply hopper and the overflow conduit at points below the top of the hopper and the normal inlet of the overflow conduit.

6. The apparatus according to claim 5 wherein a gate is provided between the supply hopper and the blasting means, and a gate is provided in the overflow conduit at a point below the outlet of the recirculating conduit connection.

7. The apparatus according to claim 6 wherein control means is provided for alternatingly operating the gates for the supply hopper and the hopper overflow whereby when the blasting means is in operation the gate in the hopper overflow is closed and the hopper-blasting means gate is open and whereby when the blasting means is not operating the hopper overflow gate is open and the hopperblasting means gate is closed.

8. The apparatus according to claim 7 wherein a conduit connects the hopper overflow supply gate with the separator assembiy.

9. The apparatus according to claim 1 wherein said velocity increasing means includes a blower connected to blow air into said inlet and thereby aid in increasing the speed of the air as it moves across said curtain.

10. The apparatus according to claim 3 wherein said velocity increasing means includes a blower connected to blow air into said inlet and thereby aid in increasing the speed of the air as it moves across said curtain.

References Cited in the file of this patent UNITED STATES PATENTS 1,030,515 Griffin June 25, 1912 2,210,103 Stoner Aug. 6, 1940 2,686,991 Powell et a1 Aug. 24, 1954 2,716,310 Moore Aug. 30, 1955 2,9 Le i e t 22, 1 

1. IN AN APPARATUS FOR SEPARATING BLASTANT PARTICLES FROM ADMIXTURE WITH PARTICLES OF LIGHTER MATERIALS BY SUCKING AIR ACROSS A FALLING CURTAIN OF SAID ADMIXTURE IN A SEPARATION CHAMBER TO CAUSE THE AIR TO BLOW THE LIGHTER PARTICLES MORE TO ONE SIDE OF THE CURTAIN THAN THE BLASTANT PARTICLES, AND SEPARATELY COLLECTING THE MORE DEFLECTED PARTICLES, THE IMPROVEMENT ACCORDING TO WHICH AIR VELOCITY INCREASING MEANS IS IN SAID SEPARATION CHAMBER CAUSING THE AIR SUCKED INTO SAID SEPARATION CHAMBER TO INCREASE ITS SPEED AS IT MOVES ACROSS SAID CURTAIN, SAID VELOCITY INCREASING MEANS INCLUDING AN AIR INLET FOR THE SUCKED IN AIR SAID AIR INLET BEING PROVIDED WITH A NOZZLE THAT TAPERS OVER A SUBSTANTIAL PORTION OF ITS LENGTH THAT GRADUALLY REDUCES THE CROSS SECTIONAL AREA OF THE AIR STREAM AS IT MOVES THROUGH THE NOZZLE AND THEREBY INCREASES THE SPEED OF THE AIR AS IT MOVES ACROSS THE CURTAIN. 